<nav>
  <span>
    <img src="/images/logo.png" alt="">
  </span>
  这是头部导航的复用
  <a href="/">首页</a>
  <a href="/html/cart.html">购物车</a>
</nav>
<form action="">
  <input class="input-search" type="text" placeholder="请输入搜索内容">
  <button>搜索</button>
</form>
